Cathode level adjustment means

ABSTRACT

In an electrolytic cell employing a flowing molten metal cathode, a means to adjust the level between the anodes and molten metal cathode is provided comprising a refractory block capable of being raised and lowered within the cathode metal so as to displace the same and adjust the level of the molten metal. Such a means is most suitable for making minor adjustments in a level of the cathode metal. For greater adjustments a compartment or chamber is provided for storing a quantity of cathode metal, the compartment or chamber communicating directly with the cathode metal in the electrolytic cell. A pressure of inert gas is maintained above the metal in this compartment or chamber to be varied at will to cause cathode metal to flow to or from the cell to maintain the desired level.

United States Patent [72] Inventor George G. Day

Madeira Beach, Fla.

[21] App]. No. 794,070

[22] Filed Jan. 27, 1969 [45] Patented Oct. 26, 1971 [73] Assignee F. Barry Haskett New York, N.Y.

[54] CATHODE LEVEL ADJUSTMENT MEANS [5 6] References Cited UNITED STATES PATENTS 759,798 5/1904 Blackmore 204/250 X 2,067,361 l/1937 Vivian 204/250 X 2,431,723 12/1947 Yerkes 204/220 X 3,265,606 8/1966 Marullo et al. 204/245 X FOREIGN PATENTS 63,473 11/1968 Germany 204/219 484,197 10/1929 Germany 204/245 Primary Examiner-John l-l. Mack Assistant Examiner-D. R. Valentine AttorneySherman and Shalloway ABSTRACT: In an electrolytic cell employing a flowing molten metal cathode, a means to adjust the level between the anodes and molten metal cathode is provided comprising a refractory block capable of being raised and lowered within the cathode metal so as to displace the same and adjust the level of the molten metal. Such a means is most suitable for making minor adjustments in a level of the cathode metal.

For greater adjustments a compartment or chamber is provided for storing a quantity of cathode metal, the compartment or chamber communicating directly with the cathode metal in the electrolytic cell. A pressure of inert gas is maintained above the metal in this compartment or chamber to be varied at will to cause cathode metal to flow to or from the cell to maintain the desired level.

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sum 1 [IF 2 INVENTOR GEORGE GERALD DAY PATENTEBnm 25 I9?! SHEET 2 [1F 2 INVENTOR GEORGE GERALD DAY CATHODE LEVEL ADJUSTMENT MEANS The present invention is directed to novel means for controlling or adjusting the level of the cathode metal in a horizontal electrolytic cell employing a molten metal cathode; more particularly, the present invention is directed to novel alternative or additive means for providing minor as well as greater adjustments of the level of the cathode metal in a horizontal electrolytic cell of the type which employs a flowing molten metal cathode and spaced anodes, the space between the anodes and cathode being filled with a fused electrolyte salt.

In the electrolysis of molten electrolyte salts, e.g. sodium chloride, an electric current is caused to flow from the anodes, usually graphite, through the molten salt to the cathode material. In a type of horizontal electrolytic cell with which the improved means of the present invention is concerned the cathode is generally a molten metal such as lead, tin, or a combination of metals, the cathode being such that the alkali metal released by electrolysis dissolves in the molten cathode metal.

Generally the horizontal electrolytic cells to which the present invention is primarily adapted are those capable of the electrolytic decomposition of inorganic salts at high temperatures. Such electrolytic cells generally comprise a substantially horizontal bottom surface, sidewalls, current-carrying cover, anodes in spaced relationship and connected to the cover to receive electric current therefrom, and an inorganic salt electrolyte floating on the molten metal cathode disposed on the bottom surface, the electrolyte being in contact with the anodes so that electric current passes through the electrolyte to the cathode. Cells of this type operating with an electrolyte comprising a fused inorganic salt have been known for some time. Thus, examples of such cells include the Acker cell, e.g., as described in U.S. Pat. No. 674,691, the Ashcroft cell, e.g., as described in U.S. Pat. No. 1,159,154, the Hamprecht cell employed in Germany during World War II and described in FIAT Report No. 830, as well as the early Szechtman cell as described for example in U.S. Pat. No. 3,104,213.

Horizontal electrolytic cells of the type in accordance with the present invention have provisions for the circulation of the cathode metal from the cell to suitable equipment for the separation of dissolved alkali metal through distillation or similar process with the return of the cathode metal to the cell. Generally, if a convective circulating system is utilized, it must be designed so that there is little loss of head. This rules out the use of an overflow system for controlling the level of cathode metal in the cell since the loss of head associated therewith could not be tolerated within the elecrolytic cell system contemplated.

While such an overflow system cannot be employed to control the level of the cathode metal in the horizontal electrolytic cell, the level of the cathode metal in the cell must be controlled in another manner so as to maintain a definite gap between the anodes and the cathode metal. This is true since optimum efficiency of the electrolytic cell can occur only where the gap between the anodes and the cathode metal is controlled or adjusted to that point where optimum resistance to passage of the electric current occurs.

Generally, variations in the total volume of the cathode metal within the electrolytic cell occur due to minor changes in composition and temperature as well as a loss of some cathode metal with the distillation of the alkali metal therefrom. Accordingly, it is necessary to compensate for these changes in the total volume of cathode metal in order to provide the best operation of the electrolytic cell.

Therefore, it has long been a desire of the industry to provide a simple and efficient means for effectively controlling the level of the cathode metal in horizontal electrolytic cells, both with respect to making minor adjustments as well as larger adjustments in the level of the cathode. Until the development of the present invention however, no simple yet efficient means for providing such necessary control or adjustment had yet been developed.

This need, however, has been fulfilled in accordance with the present invention where means is provided for controlling or adjusting the level of the cathode metal in horizontal electrolytic cells. A first embodiment of such means, particularly adapted for making minor adjustments in the level of the cathode metal comprises a displacement block so situated within the pool of cathode metal and controlled from outside of the electrolytic cell that simply raising or lowering such block produces minor changes in the level of the cathode metal.

A second embodiment of the present invention, particularly adapted for making slightly greater changes in the level of the cathode metal comprises a compartment or chamber storing a quantity of cathode metal and communicating directly with the cathode metal in the electrolysis compartment of the electrolytic cell. A pressure of inert gas is maintained above the metal in this compartment or chamber which may be varied at will to cause cathode metal to flow to or from the electrolytic cell so as to maintain the desired level.

It is accordingly a principal object of the present invention to provide novel means for controlling or adjusting the level of the cathode metal in horizontal electrolytic cells in a manner not heretofore contemplated by the prior art and in a manner which fulfills a long felt need in this area.

A further object of the present invention is to provide a novel means for making small adjustments in the level of the cathode metal in horizontal electrolytic cells through the use of a displacement block, the raising or lowering of which is effective in controlling or adjusting the level of the cathode metal.

A still further object of the present invention comprises novel means for effecting greater control or larger adjustments of the level of the cathode metal in the horizontal electrolytic cell, such means comprising a compartment or chamber containing a quantity of cathode metal, such metal being added to or taken from the main electrolytic cell through the pressure of an inert gas maintained above the metal in the compartment or chamber.

Still further objects and advantages of the novel means for adjustment the cathode level in a horizontal electrolytic cell will become more apparent from the following more detailed description thereof in connection with the accompanying drawings wherein:

FIG. 1 is a diagrammatic representation of a horizontal electrolytic cell employing the novel cathode level adjustment means of the present invention;

FIG. 2 is an enlarged view of the novel cathode level adjustment means of FIG. 1;

FIG. 3 is a diagrammatic representation of a horizontal electrolytic cell employing an alternative cathode metal level adjustment means of the present invention;

FIG. 4 is an enlarged view of the cathode metal adjustment means of FIG. 3.

In the various figures like numerals represent like elements throughout.

A suitable horizontal electrolytic cell apparatus is indicated in FIG. 1. A system is shown comprising a cell body 1 comprising a current carrying top 3, a substantially horizontal bottom 5 and sidewalls 7. The anodes 9 are connected through anode stems 11 in electrical contact with the cover 3 of the electrolytic cell. The anodes 9 are fully or partially immersed in a molten electrolyte 13 on top of a flowing molten cathode metal 15. The optimum distance between the bottom of the anodes 9 and the top surface of the flowing molten metal cathode 15 is designated as A.

In operating the electrolytic cell electric current passes from positive buss 17 through the cell cover 3 to the anodes 9 and through the electrolyte 13 thereby decomposing the same into its constituent elements. In the case of the electrolysis of fused sodium chloride the passage of the electric current through such fused electrolyte decomposes the salt into sodium and chlorine. The electric current subsequently passes through the flowing molten cathode l5 and the electrolytic cell bottom through negative buss 19. During the operation of such electrolytic cell the chlorine which is produced passes upward and is collected in a space above the anodes from where it is subsequently withdrawn, cooled and compressed for further processing, etc. The alkali metal, i.e., sodium, dissolved in a cathode metal forming an alloy therewith. Thus, in a case where in the cathode metal 15 comprises lead and the electrolyte salt 13 is fused sodium chloride an alloy of lead and sodium will be formed from the decomposition of the electrolyte.

The removal of the sodium metal from the alloy of sodium and lead for example can be achieved by a recirculation process by which the alloy rises through a pipe 21 to a distillation or flash vaporiation chamber 23 through the action, for example, of a vacuum maintained in chamber 23 from a vacuum system, not illustrated. In such a system sodium vapor is flashed from the alloy and passes out through line 25 to a condensor and further processing apparatus, not illustrated.

The density of the alloy increases due to the loss of sodium and the lowering of the temperature so that the alloy then flows out through line 25- and returns to the electrolytic cell. Therefore, if the system remains in exact balance it will continue to operate as described maintaining the proper gap A between the anodes 9 and the cathode 15. However, if the sodium vaporized in chamber 23 is less than the sodium formed in the electrolysis of the sodium chloride, the sodium content of the alloy will increase, thereby increasing the volume of alloy in circulation and the anode gap A will decrease, even possible decreasing to the point of causing a short circuit. Furthermore, if the sodium is vaporized in chambers 23 more rapidly than it is formed in the electrolysis of the fused sodium chloride the volume of the cathode metal 15 will decrease and accordingly the gap A between the anode 9 and the cathode 15 will become greater than desired for the most advantageous electrolysis of the fused electrolyte salt.

The means to control or adjust the space A between the anode 9 and cathode 15 in accordance with one embodiment with'the present invention is shown in FIGS. 1 and 2 as comprising a displacement block 27 situated so as to be capable of being lowered and raised so that varied amounts of the block 27 are immersed within the flowing molten cathode 15. The displacement block 27 can be formed of any material which is inert to the cathode and electrolyte materials to which the displacement block 27 can be made of suitable refractory material, i.e., a suitable magnesia, alumina, or similar refractory material, graphite, or any other suitable inert material.

Any suitable means can be provided to effect the raising or lowering of the displacement block 27 within the electrolytic cell. Thus, for example, as shown in FIGS. 1 and 2 a suitable means can comprise a screw 29 manually turned by handle 31 situated exterior of the electrolytic cell. Instead of the screwtype means 29 illustrated in FIGS. 1 and 2 it is of course obvious that other equivalent means for raising or lowering the dis placement block can be advantageously utilized. Thus, for example, a ratchet-type means allowing the incremental raising or lowering of the displacement block 27 has been illustrated in the FIGS. 1 and 2 as a regularly shaped block the same need not have any special configuration. Here again the displacement block 27 may be cylindrical, round, polygonal or any other shape desired. Similarly while the raising and lowering of the displacement block 27 has been illustrated in FIGS. 1 and 2 as being accomplished by the manual turning of lever or arm 31 it is of course obvious that such raising or lowering of displacement block 27 can be made automatic as through the use of a conventional electric or gas-driven motor in conjunction with a displacement block 27, thereby allowing for the incremental raising or lowering of the same.

While not shown in FIGS. 1 and 2, the apparatus of the present invention can alternatively contain a conventional hydraulic seal between the displacement block 27 and screw means 29. The use of the hydraulic seal is advantageous since this eliminates an otherwise conventional packed joint. Any conventional type of hydraulic seal arrangement can be employed in accordance with the apparatus of the present invention.

In accordance with the present invention if the gap A becomes to large for a most efiective electrolysis process it is only necessary to lower the displacement block 27 into the pool of cathode metal 15 so that by displacing a small amount of cathode metal the level of the same is increased to a point of which gap A again becomes that which produces optimum results. Likewise where the gap A becomes too small and a short circuit even becomes possible, it is only necessary to raise the displacement block 27 a minor amount so that the level of the cathode metal 15 becomes lower and gap A again becomes that which produces optimum results in the electrolysis process.

As indicated previously this embodiment of the present invention is particularly adapted where only a minor adjustment or control in the level of the cathode metal is required and the distance between the anodes and cathode is to be only adjusted to a minor extent. In accordance with the present invention the minor adjustments is meant to embrace an adjustment of up to about one-quarter inch, preferably from about oneeighth to one-quarter inch.

A further embodiment of the present invention is illustrated in FIGS. 3 and 4, FIG. 4 being an enlarged view of a novel cathode level adjustment system of this embodiment of the present invention.

In accordance with this embodiment of the present invention a compartment or chamber 41 is provided for storing a quantity of cathode metal 15 exterior of the main electrolytic cell wherein electrolysis of the used electrolyte salt is contacted. A supply of inert gas 42 is maintained above the cathode metal 15 in compartment or chamber 41, the pressure of the inert gas 42 being such as to allow withdrawal of cathode metal or addition of cathode metal to the electrolytic cell through line 43. Thus, the inert gas may be placed under a superatmosphere pressure so that some cathode metal 15 is forced into the electrolytic cell through line 43. Similarly, a subatmosphere pressure can be drawn through vacuum so that some cathode metal 15 will flow from the electolytic cell to compartment or chamber 41.

The inert gas which is used to force a withdrawal cathode 15 into electrolytic cell and thus control or adjust the gap A between the anodes 9 and cathode metal 15 may suitably comprise nitrogen or any other gas inert to the electrolysis system. Thus, for example, suitable gases can comprise nitrogen, argon, helium, methane, ethane, carbon dioxide, etc.

In accordance with this embodiment of the present invention, nitrogen or other inert gas may be forced into or withdrawn from the space above the cathode metal 15 in compartment or chamber 41 through line 45, connected to both a source of inert gas 49 and a vacuum pump 51 with pressure controller 47 operatively situated along line 45 to operatively control the pressure of the inert gas above the cathode metal. The control of the level of the cathode metal 15 in the electrolytic cell can of course be controlled manually or through the operating function of an electric level-sensing probe within the cell itself. This, of course, is a matter of expediency well known in the art of sensing the level of liquids and similar materials. The withdrawal of inert gas to chamber or compartment 41 or the introduction of inert gas to chamber or compartment 41 can, of course, be easily controlled through the manual operation of a valve 53, for example, located so that either the vacuum pump 51 or supply of inert gas 49 is operatively within the system.

In accordance with this embodiment of the present invention the means described is particularly adapted for controlling or adjusting the space between the anodes and cathode metal when a larger degree of adjustment is required. Thus, while this embodiment of the present invention can be used for making small adjustments, i.e., as little as one-eighth inch, in the level of the cathode metal it is most readily used when the cathode level must be raised or lowered by an amount of up to 1 linch or more. Advantageously, a system can be provided which contains both the displacement block as illustrated in FIGS. 1 and 2 and the exterior chamber or compartment as shown in FIGS. 3 and 4. In this way it is possible to provide the displacement block for making only very slight adjustments or corrections in the level of the cathode metal so as to keep the space between the anodes and cathode metal as its optimum distance while the exterior supply of cathode metal can be used for larger adjustments when necessary. Accordingly, while the embodiments of the present invention had been discussed alternatively it is, of course, obvious that they can be employed additively in accordance with the present invention.

Similarly, while the present invention has been described primarily with respect to a natural circulation system for the distillation and removal of alkali metal from the alkali metalcathode metal alloy it is, of course, obvious that other conventional forced systems are within the scope of the present invention. In this regard, it is pointed out that the present invention is not predicated upon the use of any particular type of electrolytic cell but is predicated upon the novel means to provide a control or adjustment of the gap or space between the anodes and cathode employed in the electrolysis of electrolyte materials. It is within this environment that the improved means of adjusting or controlling the level of cathode metal within the electrolytic cell has been developed.

lclaim:

1. In a horizontal electrolytic cell comprising a substantially horizontal bottom surface, sidewalls, current-carrying cover, anodes in spaced relationship and connected to said cover to receive electric current therefrom, and said bottom surface adapted to support an inorganic salt electrolyte floating on a molten metal cathode, the electrolyte being in contact with the anodes so that electric current passes through said electrolyte to. said cathode, the improvement which comprises means for effecting adjustment of the level of the cathode metal comprising a displacement block composed of a material inert to the environment of the electrolytic cell, and means associated with said displacement block to efiect a raising and lowering of the same within the electrolytic cell, so that by varying the amount by which said displacement block is immersed in said cathode metal the level of said cathode metal can be varied.

2. The horizontal electrolytic cell of claim 1 wherein said displacement block is composed of a refractory material.

3. The horizontal electrolytic cell of claim 1 wherein said means to raise and lower said displacement block comprises a screwed-type means manually operated from exterior the electrolytic cell.

4. In a horizontal electrolytic cell comprising a substantially horizontal bottom surface, sidewall, current-carrying cover, anodes in spaced relationship and connected to said cover to receive electric current therefrom, said bottom surface adapted to support an inorganic salt electrolyte floating on a molten metal cathode, the electrolyte being in contact with the anodes so that electric current passes through said electrolyte to said anode, the improvement which comprises means to adjust the level of the cathode metal in said electrolytic cell comprising an exterior compartment for storing a quantity of cathode metal less than the volume of said exterior compartment so as to create a space above said cathode metal in said exterior compartment filled with a gas which inert to the electrolytic process and communicating with the cathode metal in said electrolytic cell, and means communicating with said space above said cathode metal in said exterior compartment to vary the pressure of said inert gas to thereby vary-the level of the cathode metal in said electrolytic cell and exterior compartment.

5. The horizontal electrolytic cell of claim 4 wherein the pressure of the inert gas is varied by alternative engagement with a means to supply further inert gas and means to withdraw the same from said exterior compartment.

6. The horizontal electrolytic cell of claim 4 wherein said inert gas is nitrogen.

t t l 

2. The horizontal electrolytic cell of claim 1 wherein said displacement block is composed of a refractory material.
 3. The horizontal electrolytic cell of claim 1 wherein said means to raise and lower said displacement block comprises a screwed-type means manually operated from exterior the electrolytic cell.
 4. In a horizontal electrolytic cell comprising a substantially horizontal bottom surface, sidewalls, current-carrying cover, anodes in spaced relationship and connected to said cover to receive electric current therefrom, said bottom surface adapted to support an inorganic salt electrolyte floating on a molten metal cathode, the electrolyte being in contact with the anodes so that electric current passes through said electrolyte to said anode, the improvement which comprises means to adjust the level of the cathode metal in said electrolytic cell comprising an exterior compartment for storing a quantity of cathode metal less than the volume of said exterior compartment so as to create a space above said cathode metal in said exterior compartment filled with a gas which inert to the electrolytic process and communicating with the cathode metal in said electrolytic cell, and means communicating with said space above said cathode metal in said exterior compartment to vary the pressure of said inert gas to thereby vary the level of the cathode metal in said electrolytic cell and exterior compartment.
 5. The horizontal electrolytic cell of claim 4 wherein the pressure of the inert gas is varied by alternative engagement with a means to supply further inert gas and means to withdraw the same from said exterior compartment.
 6. The horizontal electrolytic cell of claim 4 wherein said inert gas is nitrogen. 